DOCUMENT:Q165915 09-AUG-2001 [winnt] TITLE :Explanation of Jet Database for Windows NT 4.0 PRODUCT :Microsoft Windows NT PROD/VER:WinNT:4.0 OPER/SYS: KEYWORDS:kbinfo kbArtTypeINF ====================================================================== ------------------------------------------------------------------------------- The information in this article applies to: - Microsoft Windows NT Server version 4.0 ------------------------------------------------------------------------------- SUMMARY ======= Windows Internet Name Service (WINS) produces J.log files in the %SystemRoot%\System32\Wins folder to increase the speed and efficiency of storing the WINS data. This article discusses these Jet files and their purpose. MORE INFORMATION ================ J.log Files -------------- To increase speed and efficiency of data storage, the Jet database writes current transactions to log files rather than to the database directly. Therefore, the most current view of the data will be the database plus any transactions in the log file(s). These files are also used for recovery if the WINS service is stopped abruptly or in an unexpected manner. If the service is stopped in an unexpected manner, the log files will automatically be used to re-create the correct state of the WINS database. Log files will always be a certain size; however, they can grow quickly in number on a very busy WINS Server. It is inevitable that WINS will write more transactions to a log than the size of the log can accommodate. When a log file becomes filled, it is renamed to indicate that it is an older log and not in use. A new transaction log is created with the J.log filename, where is a decimal number such as J50.log. The naming format of the previous log file will be JetXXXXX.log, where each X denotes a hexadecimal number from 0 to f. Previous log files are maintained in the same folder as the current log files. The log files are processed (all log entries written to the database) and deleted when a successful backup occurs or when the WINS server is shut down gracefully. Therefore, if many J.log files have accumulated, frequent backups should be scheduled to maintain the logs. After the entries have been processed, it is possible to manually delete the log files; however, this will prevent a successful recovery of the database if it should be needed. Because of this, it is important to ensure that the log files are not manually deleted or removed from the system until a backup has been performed. J.chk Files -------------- Jet maintains a checkpoint file, J.chk, that indicates the location where the last information was successfully written from the transaction logs to the database. It is also used for recovery purposes; that is, the checkpoint file indicates where the recovery or replaying of data should begin. This checkpoint file is updated every time data is written to the database file (Wins.mdb). Res1.log and Res2.log Files --------------------------- Reserved logs (Res1.log and Res2.log) are kept for emergency purposes. More specifically, they are used in the event that the server runs out of disk space. If a server attempts to create another transaction log file and there is insufficient disk space, the server will flush any outstanding transactions into these reserved log files. The service will then shut down and log an event to the Event Viewer. ====================================================================== Keywords : kbinfo kbArtTypeINF Technology : kbWinNTsearch kbWinNT400search kbWinNTSsearch kbWinNTS400search kbWinNTS400 Version : WinNT:4.0 Issue type : kbinfo ============================================================================= THE INFORMATION PROVIDED IN THE MICROSOFT KNOWLEDGE BASE IS PROVIDED "AS IS" WITHOUT WARRANTY OF ANY KIND. MICROSOFT DISCLAIMS ALL WARRANTIES, EITHER EXPRESS OR IMPLIED, INCLUDING THE WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE. IN NO EVENT SHALL MICROSOFT CORPORATION OR ITS SUPPLIERS BE LIABLE FOR ANY DAMAGES WHATSOEVER INCLUDING DIRECT, INDIRECT, INCIDENTAL, CONSEQUENTIAL, LOSS OF BUSINESS PROFITS OR SPECIAL DAMAGES, EVEN IF MICROSOFT CORPORATION OR ITS SUPPLIERS HAVE BEEN ADVISED OF THE POSSIBILITY OF SUCH DAMAGES. SOME STATES DO NOT ALLOW THE EXCLUSION OR LIMITATION OF LIABILITY FOR CONSEQUENTIAL OR INCIDENTAL DAMAGES SO THE FOREGOING LIMITATION MAY NOT APPLY. Copyright Microsoft Corporation 2001.